<template>
<!-- 分页器组件 -->
  <div class="pagination">
    <!-- 上 -->
    <button 
    @click="$emit('getCurrentPage',pageNo - 1)"
    :disabled = "pageNo === 1"
    >
      上一页
    </button>
    <button v-if="startOrEnd.start > 1"
      @click="$emit('getCurrentPage',1)"
      :class="{active:pageNo === 1}"
      >
      1
    </button>
    <button v-if="startOrEnd.start > 2">···</button>
    <!-- 中间部分 -->
    <button
    v-for="(page,index) in startOrEnd.end" :key='index'
    v-if="page >= startOrEnd.start"
    @click="$emit('getCurrentPage',page)"
    :class="{active:pageNo === page}"
    >
     {{page}}
    </button>
    <!-- 下 -->
    <button v-if="startOrEnd.end <totalPage - 1">···</button>
    <button v-if="startOrEnd.end < totalPage"
    @click="$emit('getCurrentPage',totalPage)"
    :class="{active:pageNo == totalPage}"
    >
    {{totalPage}}
    </button>
    <button
    @click="$emit('getCurrentPage',pageNo + 1)"
    :disabled ="pageNo === totalPage"
    >
      下一页
    </button>
    <button 
    style="margin-left: 30px"
    >共 {{total}} 条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  /* 
  pageNo -- 当前页
  pageSize -- 每页条数
  total -- 总条数
  continues -- 连续数字
  */
  props:['pageNo','pageSize','total','continues'],
  computed:{
    //一共多少页
   totalPage(){
      //向上取整
      return Math.ceil(this.total/this.pageSize)
    },
    //连续的起始页和结束页
    startOrEnd(){
      const {pageNo,total,continues,totalPage} = this
       let start = 0
       let end = 0
       if(continues > total){
         //不正常现象
         start = 1
         end =totalPage
       }else{
         //正常现象 (当前页 - 连续页数/2 然后再取整 )
         start = pageNo - parseInt(continues/2)
         end = pageNo + parseInt(continues/2)
        //把出现不正常现象的[start为0|负数]纠正
         if(start < 1){
           start = 1
           end = continues
         }
         //把出现不正常现象的[end 大于总页码数]纠正
         if(end > totalPage){
           start = totalPage - continues + 1
           end = totalPage
         }
       }
       return {start,end}
    }
  }
};
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.active{
  background: skyblue;
}
</style>